Using the utilization experience of an H.M.O. (a prepaid comprehensive health service delivery system, Kaiser (Potland), the proposed research will: a) Carry out descriptive and analytic studies on the utilization experience on this defined population in terms of: prevalnce and incidence studies on the cohort exprience of the study population with respect to morbidities; etiology disease; provider behavior; and alternative methods of the classification of disease. b) Two studies that explore the: 1) The economic implication of the diagnosis-specific costs related to physicians and services. 2) The sociologic implictions of family utilization and the relation to social-psychological factors and health status factors. The proposed research has as its focus a structured study examining the broad spectrm of factors bearing on utilization, an an economic and sociologic study set within a multidisciplinary context. The study employs the 1967-70 utilization data base of the Kaiser (Portland) membership study. The ambulatory care, inpatient, and the membership (person-months) Calendar File are used to link together the total utilization spectrum of an ongoing, longitudinal 5 percent Sample. These data are supplemented by a househod interview survey. This study represents a collaborative reserach related to specific questions.